Exploration of laser-driven electron-multirescattering dynamics in high-order harmonic generation

Abstract

Multiple rescattering processes play an important role in high-order harmonic generation (HHG) in an intense laser field. However, the underlying multi-rescattering dynamics are still largely unexplored. Here we investigate the dynamical origin of multiple rescattering processes in HHG associated with the odd and even number of returning times of the electron to the parent ion. We perform fully ab initio quantum calculations and extend the empirical mode decomposition method to extract the individual multiple scattering contributions in HHG. We find that the tunneling ionization regime is responsible for the odd number times of rescattering and the corresponding short trajectories are dominant. On the other hand, the multiphoton ionization regime is responsible for the even number times of rescattering and the corresponding long trajectories are dominant. Moreover, we discover that the multiphoton- and tunneling-ionization regimes in multiple rescattering processes occur alternatively. Our results uncover the dynamical origin of multiple rescattering processes in HHG for the first time. It also provides new insight regarding the control of the multiple rescattering processes for the optimal generation of ultrabroad band supercontinuum spectra and the production of single ultrashort attosecond laser pulse.

Dynamics of tunneling ionization using Bohmian mechanics

“…The present study is devoted to a description of tunneling ionization employing Bohmian Mechanics [11][12][13], which has recently attracted much attention [14][15][16][17][18][19][20][21][22][23][24]. It will be shown that computing the streamlines of the wavefunction probability over time provides valuable insights and a natural route to understanding complex ultrafast mechanisms.…”

Effect of multiple rescatterings on continuum harmonics from asymmetric molecules in multicycle lasers

“…6,11,12 For long laser wavelengths, the HOR can have stronger manifestations in the HHG. 11,[13][14][15][16][17][18][19][20][21] Especially in ref. 6 for helium atom, it is proposed that targets illuminated by few-cycle mid-infrared laser pulses can generate zeptosecond pulses due to the interference between the first-and third-order return trajectories.…”

“…Despite the difference between the two proposals (interference vs. reducing HOR schemes), they are examples of electron trajectory manipulation, the method is known before to generate attosecond pulse trains (APT). [22][23][24][25][26] As mentioned above, until now, most HOR studies just focused on atomic systems 6,9,11,[15][16][17]19,21 or simple molecules such as H 2 + 18,20 and usually relied on the strong-field approximation. 6,9,15,21 The pulses commonly used in the literature are also quite long, of five cycles or longer 9,18,19,21 (except for the work 6 ).…”

Single-electron quantum dynamics in high-harmonic generation spectrum from LiH molecule: Analysis of potential energy surfaces for electrons constructed from a model of localized Gaussian wave packets with valence-bond spin-coupling

“…Treating many electrons will add further complexities where adequacy of the mean-field orbital picture is not obvious. Consequently, computational studies of electron dynamics under strong field on realistic molecular models are rather scarce (although the reference list herein [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] is not exhaustive). The size of the molecules that have been treated so far is also limited.…”